Mobile telephones have traditionally been voice-centric devices with proprietary operating systems handling all communication tasks. The Application Programming Interfaces (APIs) in these devices were not made available to third-party developers. As a consequence, end users were dependent on the device manufacturers for applications.
Today, the mobile communications industry is increasingly becoming aware of the importance and benefits of open application environments for mobile devices. Basically, an open application environment permits the installation of third party applications on the mobile device during device manufacture or later on by a user operating the device. Such third party applications include games, software upgrades, etc.
A. Ghosh et al., “Open application environments in mobile devices: Focus on JME and Ericsson Mobile Platforms”, Ericsson Review No. 2, Vol. 82, 2005, pages 82 to 91 (ISSN: 0014-0171) describe an exemplary open application environment for mobile devices. The open application environment is based on a mobile platform with a digital baseband processor supporting wireless NATs, so-called radio access technologies (RATs), such as General Packet Radio Service (GPRS), Enhanced Data for GSM Evolution (EDGE) or Wideband Code-Division Multiple Access (WCDMA). A mobile platform is an environment that includes all the necessary integrated circuits and software needed to provide wireless network access services and communication services (e.g. for voice, data or multimedia applications), as well as interfaces to make these services available to applications residing on the mobile platform.
In the open application environment described by A. Ghosh et al., dedicated middleware services are provided to allow an application-based control of platform-internal functionalities such as the resolution and the encoding of data streams. These middleware services include an API (the so-called Open Platform API, or OPA) that is structured into various well-defined categories. This structure of the OPA makes it easy for an application programmer to locate and address platform-specific functionalities.
Conventionally, mobile platforms often included proprietary Operating Systems (OS). Now, with the advent of the open application environment, an application platform with a third-party application processor will be added to the mobile device when it is desired to run an open OS such as Symbian. The application platform will be co-located with the mobile platform in the mobile device and handle all applications including, for example, multimedia applications. The mobile platform, on the other hand, will be in charge of a reduced set of functionalities (including all mobile communications tasks such as wireless network access) and mainly act as a network access platform. Between the application platform and the mobile platform an interface mechanism provides the applications on the application platform with access (via OPA) to platform-internal functionalities of the mobile platform as if the applications resided directly on the mobile platform.
In some cases it may be necessary or desirable to equip a mobile device with more than one NAT. In this regard, WO-A-00/22857 teaches a modular approach in which different network access platforms in the form of so-called network access modules (such as a Local Area Network (LAN) module and a Global System for Mobile communications (GSM) module) are interconnected via a communication bus according to the Universal Serial Bus (USB) standard. Other modules connected to the communication bus such as a Closed-Circuit Television (CCTV) module may then selectively transmit signals via the LAN module on the one hand or via the GSM module on the other.
It has been found that it would be advantageous to let network access platforms communicate directly with each other. Such a direct communication is desirable to implement low-level control mechanisms for example in context with handover signalling between the network access platforms. Moreover, it may in certain cases be desirable to make such inter-platform communication concepts compatible with open application environments.